package com.wc.alorithm_luogu.P5722;

import java.util.Scanner;

/**
 * @Author congge
 * @Date 2023/4/20 11:39
 * @description https://www.luogu.com.cn/problem/P5722
 * 数列求和
 */
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();

        int sum = n * (n + 1) / 2;
        System.out.println(sum);
    }
}
